Mastersound Tube amp

Trying to swap 845 tubes on Mastersound 845 Compact amp but having difficulty removing the 845 tube. I don't want to use excessive force just in case there is a specific way of doing it. 
Does anyone know exactly how to do this? The manual is completely useless here. Does it need to be turned in a particular direction before pulling out? 

I tried contacting the distributor but have not heard back yet.